Hydrophilic, aliphatic polyurethane foams

Abstract

The invention relates to a method for producing hydrophilic, aliphatic polyurethane foams. The invention further relates to special compositions for producing polyurethane foams either using the method according to the invention or using the polyurethane foams obtained from the compositions according to the invention, and to the use of the polyurethane foams as a wound dressing, cosmetic item, or incontinence product.

The invention claimed is: 
     
       1. A process for producing a hydrophilic aliphatic polyurethane foam, which comprises providing a composition comprising
 A) isocyanate-functional prepolymers obtained by reaction of
 A1) low molecular weight aliphatic diisocyanates having a molar mass of 140 to 278 g/mol with 
 A2) di- to hexafunctional polyalkylene oxides having an OH number of 22.5 to 112 mg KOH/g and an ethylene oxide content of 50 to 100 mol %, based on the total amount of oxyalkylene groups present, 
 
 B) alkali metal salts of weak inorganic acids, wherein the alkali metal salts of weak inorganic acids B) are selected from the group consisting of potassium hydroxide, potassium carbonate, sodium hydroxide, sodium bicarbonate, sodium carbonate, and mixtures thereof, 
 C) water, 
 D) heterocyclic 4-ring or 6-ring oligomers of low molecular weight aliphatic diisocyanates having a molar mass of 140 to 278 g/mol, 
 E) optionally catalysts different from B), 
 F) optionally surfactants, 
 G) optionally mono- or polyhydric alcohols, and 
 H) hydrophilic polyisocyanates obtained by reaction of
 H1) low molecular weight aliphatic diisocyanates having a molar mass of 140 to 278 g/ml and/or polyisocyanates obtained therefrom with an isocyanate functionality of 2 to 6, with 
 H2) monofunctional polyalkylene oxides having an OH number of 10 to 250 and an ethylene oxide content of 50 to 100 mol %, based on the total amount of oxyalkylene groups present, 
 
 foaming and curing the composition. 
 
     
     
       2. The process as claimed in  claim 1 , wherein the alkali metal salts of weak inorganic acids B) are selected from the group consisting of sodium hydroxide, sodium bicarbonate and sodium carbonate. 
     
     
       3. The process as claimed in  claim 1 , wherein isocyanate-functional prepolymers A) having a weight fraction of below 1.0 wt % for low molecular weight aliphatic diisocyanates having a molar mass of 140 to 278 g/mol, based on the prepolymer, are used. 
     
     
       4. The process as claimed in  claim 1 , wherein the components A) to H) are used in the following amounts:
 A) 100 parts by weight of isocyanate-functional prepolymers, 
 B) 0.01 to 5 parts by weight of alkali metal salts of weak inorganic acids, 
 C) 0.1 to 200 parts by weight of water, 
 D) up to 100 parts by weight of heterocyclic oligomers, 
 E) 0 to 1 part by weight of catalysts, 
 F) 0 to 10 parts by weight of surfactants, 
 G) 0 to 20 parts by weight of mono- or polyhydric alcohols, and 
 H) up to 60 parts by weight of hydrophilic polyisocyanates. 
 
     
     
       5. The process as claimed in  claim 4 , wherein the composition comprises 10 to 100 parts by weight of heterocyclic oligomers D). 
     
     
       6. The process as claimed in  claim 4 , wherein the composition comprises 20 to 90 parts by weight of heterocyclic oligomers D). 
     
     
       7. The process as claimed in  claim 4 , wherein the composition comprises 20 to 80 parts by weight of heterocyclic oligomers D). 
     
     
       8. The process as claimed in  claim 1 , wherein the low molecular weight aliphatic diisocyanates A1) are hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI) or mixtures thereof. 
     
     
       9. The process as claimed in  claim 1 , wherein the polyalkylene oxides A2) are copolymers of ethylene oxide and propylene oxide having an ethylene oxide content, based on the total amount of oxyalkylene groups present, of 60 to 85 mol %, and started on polyols or amines. 
     
     
       10. The process as claimed in  claim 1 , wherein the polyalkylene oxides A2) have number-average molecular weights of 3000 to 8500 g/mol. 
     
     
       11. The process as claimed in  claim 1 , wherein the polyalkylene oxides A2) have OH functionalities of 3 to 4. 
     
     
       12. The process as claimed in  claim 1 , wherein no catalysts E) are used. 
     
     
       13. A composition comprising
 A) isocyanate-functional prepolymers, having a weight fraction of below 1.0 wt % for low molecular weight aliphatic diisocyanates having a molar mass of 140 to 278 g/mol, based on the prepolymer, obtained by reaction of
 A1) low molecular weight aliphatic diisocyanates having a molar mass of 140 to 278 g/mol with 
 A2) di- to hexafunctional polyalkylene oxides having an OH number of 22.5 to 112, and an ethylene oxide content of 50 to 100 mol %, based on the total amount of oxyalkylene groups present, 
 
 B) alkali metal salts of weak inorganic acids, wherein the alkali metal salts of weak inorganic acids B) are selected from the group consisting of potassium hydroxide, potassium carbonate, sodium hydroxide, sodium bicarbonate, sodium carbonate, and mixtures thereof, 
 C) water, 
 D) heterocyclic 4-ring or 6-ring oligomers of low molecular weight aliphatic diisocyanates having a molar mass of 140 to 278 g/mol, 
 E) optionally catalysts different from B), 
 F) optionally surfactants, 
 G) optionally mono- or polyhydric alcohols, and 
 H) hydrophilic polyisocyanates obtained by reaction of
 H1) low molecular weight aliphatic diisocyanates having a molar mass of 140 to 278 g/ml and/or polyisocyanates obtained therefrom with an isocyanate functionality of 2 to 6, with 
 H2) monofunctional polyalkylene oxides having an OH number of 10 to 250 and an ethylene oxide content of 50 to 100 mol %, based on the total amount of oxyalkylene groups present. 
 
 
     
     
       14. The composition as claimed in  claim 13 , wherein component A2) are tri- to hexafunctional polyalkylene oxides having an OH number of 31.5 to 56, and an ethylene oxide content of 60 to 85 mol %, based on the total amount of oxyalkylene groups present. 
     
     
       15. The composition as claimed in  claim 13 , wherein the alkali metal salts of weak inorganic acids B) are selected from the group consisting of sodium hydroxide, sodium bicarbonate and sodium carbonate. 
     
     
       16. The composition as claimed in  claim 13  wherein the components A) to H) are present in the composition in the following amounts:
 A) 100 parts by weight of isocyanate-functional prepolymers, 
 B) 0.01 to 5 parts by weight of alkali metal salts of weak inorganic acids, 
 C) 0.1 to 200 parts by weight of water, 
 D) up to 100 parts by weight of heterocyclic oligomers, 
 E) 0 to 1 part by weight of catalysts, 
 F) 0 to 10 parts by weight of surfactants, 
 G) 0 to 20 parts by weight of mono- or polyhydric alcohols, and 
 H) up to 60 parts by weight of hydrophilic polyisocyanates. 
 
     
     
       17. A polyurethane foam obtained by the process as claimed in  claim 1 . 
     
     
       18. A primary wound dressing, a cosmetic article or an incontinence product comprising the polyurethane foam as claimed in  claim 17 .